Railcar draft gears have been used for many years at opposite ends of a railcar to absorb and cushion impact forces. During assembly of a train consist, the impact loads and forces between two railcars can be substantial. That is, during assembly of a train consist, the impact loads between two railcars can be well in excess of 500,000 pounds. To operate in such environments, most railcar draft gears include a cast housing having an inwardly tapered bore at an open end, a spring assembly disposed within the housing, a series of metal friction shoes or members arranged in the tapered bore of the housing and movable against the spring upon compression of the draft gear, and a wedge disposed in operable combination with the friction members such that impact blows directed against the wedge are transferred axially to the spring and radially to the housing.
In earlier railcar draft gears, the spring assembly used one or more steel springs to absorb energy between two railcars. Later, the spring assembly was designed with a stacked series of individual spring units for absorbing the energy realized by the railcar draft gear; with each spring unit including a rubber spring sandwiched between two generally rectangular metal plates. More recently, other elastomeric materials have been used and accepted as replacements for steel and/or rubber springs. One elastomeric spring offering beneficial results is disclosed in U.S. Pat. No. 5,351,844 to R. A. Carlstedt and includes multiple circular or toroidally shaped elastomeric springs stacked in axial relation to each other.
Railcar manufacturers and suppliers for such railcar manufacturers are continually seeking methods and ways of enhancing spring performance while reducing manufacturing costs of railcars and the components used to build such railcars without having to sacrifice performance and quality. The draft gear housing wherein the spring is housed frequently has a generally rectangular cross-sectional configuration. As such, a circular or toroidal shape of the spring unit within a draft gear housing having a spring chamber formed with a generally rectangular cross-section in plan wastes valuable space which could otherwise be used by a spring to absorb energy. A non-circularly shaped or designed spring unit, however, also presents a unique series of challenges which are encountered during formation of the spring. Moreover, it is important for the elastomer of each spring unit to not extend or be squeezed from between the metal plates to an extent the elastomer extends beyond an outer profile of the plates and rubs or otherwise engages with the internal wall of the draft gear housing. Such rubbing contact can frequently damage the spring and adversely affect draft gear performance.
Thus, there is a continuing need and desire for a railcar draft gear spring assembly having a non-circular design which optimizes the space constraints of the draft gear housing and is capable of absorbing and dissipating the relatively high levels of energy typically encountered by a railcar draft gear during operation, then returning to its pre-operative length as the actuating force is removed from the draft gear.